The independent system operator that manages the New England power grid may be close to dealing with an emergency similar to last year’s shutdown of one of the Millstone Nuclear Power Station units.
As ISO New England warns that the current heat wave could push power usage to near record levels by Thursday, it faces the potential shutdown of the Pilgrim Nuclear Power Station in Massachusetts for the same reason Millstone Unit 2 shut down for 12 days last summer: intake water temperatures too warm to cool the plant.
The Nuclear Regulatory Commission said that Tuesday night Pilgrim reported its intake water temperature was 75.3 degrees for about an hour-and-a-half before dropping down below the permitted maximum of 75 degrees. On Wednesday, the temperature hit 75.5 for five-and-a-half hours, forcing the plant to reduce power to 85 percent. It is now back to 100 percent capacity.
Millstone was the first case of an intake water temperature-induced shutdown. Both plants, which use saltwater, had long been considered less vulnerable to water issues than have plagued inland power plants facing drought conditions.
While Pilgrim has not had to shut down, the specter that it might serves as yet another indication that climate change may have profound impacts on energy systems.
The Pilgrim situation and this week’s heat wave coincidentally come as two new reports warn of widespread vulnerabilities in the nation’s energy supply due to the cascading effects of climate change and extreme weather. 
One, from the federal Department of Energy, warns of multiple concerns that in combination can magnify and broaden impacts. Increased and more virulent storms and sea level rise can flood and otherwise damage shoreline energy facilities. Drought can lower levels and warm water, hampering or shutting down plant operations. Excessive heat can hurt electric grid efficiency at the same time it increases demand to run cooling systems. Wildfires can destroy all manner of grid and plant infrastructure. Low water levels may make renewable energy like hydro-electricity less reliable; and the water-dependent fracking process, critical to the natural gas supply could be compromised.
“It’s the recognition that there are many, many areas that need to be addressed simultaneously,” said Department of Energy and Environmental Protection Commissioner Dan Esty, who called the report “impressive.” “It’s the cumulative effect of a whole series of things occurring at once.”
The other report, Water-Smart Power from the Union of Concerned Scientists, warns of widening power problems due to difficulties with the vast amounts of water needed to operate plants, not unlike the situations at Millstone and Pilgrim.
Esty said the prospect of water and other impacts could lead to rethinking “fundamentally the electricity system and more broadly our energy infrastructure.”
To that end, Esty said he is working with the utilities to draw up lists of which facilities –- especially those on the coast and along rivers -– need to be considered priorities. Costs, he said, dictate that most will have to be retrofits -– elevating buildings and otherwise hardening them. But when units need to be replaced, then he said it would be prudent to consider moving them along with building them to withstand ongoing climate change.
The state will also be expanding its microgrid effort as one means to make the centralized electrical system less vulnerable. Esty and Gov. Dannel P. Malloy would like to see on-site electrical generation constructed for critical facilities like hospitals, shelters and police and fire stations, as well as commercial zones with grocery stores, gas stations and pharmacies so they are able to run if grid power is out.
In the next couple of weeks, those selected to receive grants through the initial microgrid pilot program will be announced. From an original pool of 36 projects -– mostly from cities and towns, 18 are still in the running. Funding to continue the program for another two years was approved by the legislature during the most recent session.
The legislature also approved a large increase in energy efficiency funding as a way to lower energy demands and it authorized DEEP to make long-term renewable power purchases.
Such efforts mirror recommendations in the DOE report, and would indicate that while Connecticut continues to have energy vulnerabilities (Esty said emphatically the lack of water for hydro is NOT one of them), the state is on track towards the key recommendations -– diversification and efficiency.
“Gains in energy efficiency and water efficiency — those are things that you can get a lot out of rather than building entirely new power plants,” said Joe Casola, a staff scientist and director of science and impacts with the Center for Climate and Energy Solutions. “Almost all forms of energy fuels and energy systems have their own sensitivities to climate in one way or another.”
But the full cascade of effects of climate change is hard to assess on energy systems. “How does that effect all the sand at the beach; how does that effect all the zoo plankton in Long Island Sound?” he asked rhetorically in terms of what impact those things might have on power plant intake valves or overall water temperature.
“Farther and farther down that equation it becomes harder and harder to predict those things.” 
Esty, for instance, remains concerned about the impact of Millstone’s discharge water -– limited to 83 degrees where it enters the Sound -– on the already warming water.
“I think it does represent an issue for Millstone going forward. They may need to develop a different cooling strategy for the water because at some point there is a real threat to marine life,” he said. “If there were an issue of once in 50 years needing to go beyond the current temperature protocol for the water discharge, it might be no big deal. But if it’s going to become a regular thing, we cannot count on that given the potential impacts on the marine ecosystem.”
Millstone spokesman Ken Holt said the plant this summer is studying the effect of warmer discharge water and how long it takes to dissipate, though not its impact on marine life. In the wake of last summer’s shutdown, Dominion, the plant’s owners, filed for a license change that would increase the intake water temperature limit to 80 degrees from its current 75. A decision will come sometime next year.
In the meantime, Holt said, intake temperatures are running around 70 degrees, slightly lower than this time last year — possibly a result of the much colder winter and cool, rainy spring this year.
For its part, ISO New England, which admits the grid here will face challenges when older and less desirable coal and oil plants are retired in the coming years, has asked all power plant owners to postpone non-essential maintenance for the duration of the heat wave so that as many facilities as possible would be available to supply power. A spokeswoman declined to comment specifically on the Pilgrim situation.
On Tuesday, ISO put out a request to the public for voluntary conservation. Thursday it revised upward its estimate for peak demand, predicting it would reach 27,900 megawatts both Thursday and Friday (1 megawatt can power 1,000 homes). That is just short of the all-time high of 28,130 megawatts needed on Aug. 2, 2006.
Esty said he is in constant contact with ISO. “I think all of us recognize that this is going to be a very challenging week from the point of view of power demand,” he said.
John Rogers, a senior energy analyst with the Union of Concerned Scientists, and lead author on its water and energy report, said flexibility, energy efficiency and diversification are the paths away from energy vulnerability in situations like the one this week.
“Make sure you’re not locked into single big large facilities that can be taken down at a particular point,” he said. And while he recognized such efforts come with large pricetags: “So does inaction. Think about what it costs to not have access to power.”
“Last summer was really a wake-up call in the Northeast,” Rogers said. “If it’s a single plant being affected we can deal with that. But if it’s more systemic and broader and with climate change, we need to be planning now; we need to be implementing now.”